A well known and convenient way of producing printed circuits includes the printing of electrically conductive tracks on a substrate, for example, using screen printing techniques. The tracks are printed using an electrically conductive ink which typically comprises a polymeric material having electrically conductive particles, for example, copper, silver or other suitable metal, dispersed in the polymeric composition. The polymeric materials are typically cured to a solid condition by subjecting them to radiation, for example, infra-red radiation or ultra-violet light.
Although the conductive inks which are used have a sufficient electrical conductivity for use in certain circumstances, the electrical conductivity has in no case been as great as the electrical conductivity of copper or other highly conductive metals. Even the conductive inks with the best performance have electrical conductivities which in most cases are only one tenth of the electrical conductivity of copper. It has been proposed to enhance the conductivity of the conductive tracks as continuous printed circuits by electro-plating the tracks with a suitable layer of metal, for example, copper but, in order to carry out electro-plating, it is necessary to have a continuous electrical circuit: that is not conveniently possible where the printed conductive tracks of a printed circuit are discrete and are not connected with one another. Furthermore, electro-plating has required the immersion of the substrate carrying the printed conductive tracks in a bath of suitable electro-plating solution: that technique restricts the substrates which can be subjected to such an immersion electro-plating technique—for example—paper based substrates are generally unsuitable as they will tend to be attacked and softened by the electro-plating solution. It has also been proposed to provide a more conductive coating on conductive tracks of printed inks by electroless plating. Electroless plating involves the use of plating solutions which are less stable than those commonly used in electro-plating and the process is less readily controlled. Furthermore, electroless plating still requires the substrate to be immersed in the plating solution with the consequent possibilities of attack of the substrate as well as being restricted in the thickness of deposit.
Thus, it would be advantageous to provide an improved method of providing conductive tracks on a printed circuit by electro-plating. It would be further advantageous to provide an improved printed circuit.